Updated: 12/12/2019

Psoriasis

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Snapshot
  • A 15-year-old boy with a history of Crohn disease who is on infliximab presents with a new rash. He reports pain preceding a new pink rash with tiny white “dots” all over his back. He has been taking infliximab for 1 year now and without issue. On physical exam, there are dozens of 1 mm pustules overlying erythematous skin with no scaling. A bacterial swab of the pustules reveal only normal skin flora. He is diagnosed with pustular psoriasis induced by infliximab. He is immediately started on other systemic therapy for both his Crohn disease and pustular psoriasis.
Introduction
  • PhotoClinical definition
    • idiopathic and chronic inflammatory disease characterized by hyperkaratosis and parakeratosis
  • Classification
    • plaque psoriasis
      • most common
      • well-defined erythematous plaques with scales
      • typically over extensor surfaces
    • inverse/intertriginous psoriasis
      • plaques with minimal scaling in skin folds
    • pustular psoriasis
      • pustules rather than plaques
    • erythrodermic psoriasis
      • generalized erythema covering almost entire body surface area
      • a medical emergency
    • guttate psoriasis
      • 1- 10 mm pink macules with scaling
  • Epidemiology
    • incidence
      • US incidence
        • 2% of population
    • demographics
      • normally, > 40 years of age but can affect people of all ages
    • risk factors
      • smoking
      • skin trauma
      • alcohol abuse
      • stress
      • cold weather
  • Etiology
    • idiopathic
    • drugs 
      • while tumor necrosis factor-alpha (TNF-α) inhibitors are a treatment for psoriasis, it can cause new-onset “paradoxical” psoriasis when used for another inflammatory disease (such as Crohn disease)
        • β-blockers may exacerbate psoriasis 
  • Pathogenesis
    • hyperproliferation of basal stem keratinocytes
    • ↑ inflammation, especially inflammatory markers IL-6, C-reactive protein, TNF-α, E-selectin, and ICAM-1
  • Associated conditions
    • psoriatic arthritis
Presentation
  • Symptoms
    • painful or pruritic skin lesions
    • joints may be painful or stiff
      • especially in feet and hands
  • Physical exam
    • plaque psoriasis
      • well-circumscribed, pink papules and flat-topped plaques with silvery scales 
      • common locations
        • scalp
        • trunk
        • buttocks
        • extensor surface of limbs
        • positive Auspitz sign
          • when scales are scraped off, there is pinpoint bleeding
            • results from exposure of dermal papillae
        • nail changes
          • pitting
        • candle-grease sign
          • when a sharp object is used to scratch a lesion, a candle-grease-like scale can be produced
        • Koebner's phenomenon
          • psoriatic lesions appear at site of cutaneous physical trauma
    • pustular psoriasis
      • sterile pustules on erythematous skin
    • guttate psoriasis
      • salmon pink papules with fine overlying scales
      • location
        • trunk
        • proximal extremities
Studies
  • Labs
    • electrolytes
      • there may be electrolyte imbalances if psoriasis is erythrodermic
  • Histology
    • acanthosis with parakeratosis (thickened stratum corneum with preserved nuclei)
    • hyperkeratosis (thickened epidermis)
    • Munro microabscesses
    • ↑ stratum spinosum
    • ↓ stratum granulosum
  • Diagnostic criteria
    • diagnosis is primarily based on clinical exam and history
Differential
  • Atopic dermatitis
  • Seborrheic dermatitis
Treatment
  • Conservative
    • emollients
      • indications
        • for all patients
  • Medical
    • topical corticosteroids
      • indications
        • first-line and often used in combination with topical calcipotriene
          • note that systemic steroids are avoided due to likely flare up of psoriasis while tapering
    • topical calcipotriene (vitamin D analog)
      • indication
        • first-line and often used in combination with topical corticosteroids
    • systemic non-biologic therapies
      • indications
        • moderate-to-severe psoriasis
        • used in combination with topical therapies
      • drugs
        • acitretin
        • methotrexate
        • cyclosporine
        • apremilast
          • especially for those with psoriatic arthritis as well
    • systemic biologic therapy
      • indication
        • moderate-to-severe psoriasis
      • drugs
        • tumor necrosis factor inhibitors
          • adalimumab
          • etanercept
          • infliximab
        • anti-interleukin agents
          • brodalumab
          • secukinumab
          • ustekinumab
    • narrowband ultraviolet B
      • indication
        • for patients who are contraindicated to systemic therapy or who want to avoid systemic side effects
Complications
  • Cardiovascular disease
    • psoriasis patients are at higher risk

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(M3.DM.16.31) A 34-year-old woman presents to the clinic complaining of a rash that appeared on her left forearm after a scratch three days ago. This is not the first time she has experienced such a rash, as the patient states she had a similar looking lesion on her elbows three years ago. Upon further questioning, she states that her older sister has had problems with her skin, but she is unsure of the diagnosis. On physical exam you find a circular and scaly, pearl-colored rash superimposed over an abrasion on her left forearm (Figure A). Of note, the patient has has the following nail appearance (Figure B). What is the diagnosis in this patient?

QID: 102785
FIGURES:
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Hypertrophic scar

0%

(0/1)

2

Abrasion

0%

(0/1)

3

Psoriasis

100%

(1/1)

4

Lichen planus

0%

(0/1)

5

Seborrheic dermatitis

0%

(0/1)

M 10 D

Select Answer to see Preferred Response

(M3.DM.15.40) A 44-year-old man presents to his family physician with complaints of dry and scaly lesions on his bilateral elbows. He reports that these lesions developed in his 20's and have been growing in size since that time. He also reports similar lesions on the anterior portion of his knees. The lesions itch and they bleed when he scratches them. He denies any additional past medical history. Physical examination reveals the lesions shown in Figure A. Additional findings include pitting of the fingernails. Which of the following medications may worsen or exacerbate this patient's condition?

QID: 102794
FIGURES:
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Infliximab

50%

(4/8)

2

Losartan

0%

(0/8)

3

Oxycodone

0%

(0/8)

4

Procainamide

0%

(0/8)

5

Propranolol

12%

(1/8)

M 11 E

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Evidence (2)
EXPERT COMMENTS (7)
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